1. Field of the Invention
The present invention relates to the process for preparing high purity inorganic higher oxides of the alkali and alkaline earth metals by subjecting the hydroxide of the alkali or alkaline earth metals to a radio frequency discharge sustained in oxygen.
Inorganic superoxides have the general formula MO.sub.2 or L(O.sub.2).sub.2 where M and L are alkali and alkaline earth metals respectively. Superoxides are strongly yellow in color and react with water in either the liquid or vapor state at ambient temperatures to generate molecular oxygen and alkaline hydroxides which can absorb carbon dioxide according to the reactions: EQU 2 MO.sub.2 (S) + H.sub.2 O (l) -- 2 MOH (S) + 3/2 O.sub.2 (g) (1) EQU 2 MOH (S) + CO.sub.2 (g) -- M.sub.2 CO.sub.3 (S) + H.sub.2 O (l) (2)
Overall: EQU 2 MO.sub.2 (S) + CO.sub.2 (g) -- M.sub.2 CO.sub.3 (S) + 3/2 O.sub.2 (g) (3)
As indicated by the above reactions a single superoxide compound can be used for supplying oxygen necessary for human respiration while simultaneously removing carbon dioxide given off as a product of that respiration. Furthermore, because of their strong oxidizing properties, superoxides can destroy air-borne bacteria and toxic or noxious materials present in the atmosphere. Superoxides are therefore ideally suited for non-regenerative air revitalization in life support systems encountered in manned space flight capsules and in submarines.
2. Description of the Prior Art
Potassium superoxide (KO.sub.2) has been available commercially for at least 30 years and has been used as an oxygen source in emergency breathing apparatus used in various rescue operations such as fire and mine accidents and military first aid. Potassium superoxide, however, has been a relatively expensive compound being priced at about $5.00/lb. since prior art methods for forming the superoxide have employed expensive starting compounds or elaborate and expensive techniques.
One prior art commercial method for the production of potassium superoxide involves the use of molten potassium metal which is atomized into a chamber filled with oxygen at 1.2 atmospheres and 300.degree. C with the superoxide product being collected at the bottom of the chamber. This prior art method for the production of superoxides is expensive since metallic potassium is used as the starting material and is hazardous since metallic potassium can react with water and air to result in a explosion. This method is also inefficient since the metallic potassium is corrosive to the apparatus.
Potassium superoxide has also been prepared by reacting potassium hydroxide with the gaseous oxygen. This prior art method has resulted in problems with purity of the superoxide produced. The purity of typical product obtained from the reaction of potassium hydroxide with oxygen at 1 atmosphere and 210.degree. C is 20% which increases to 34% at a temperature of 510.degree. C.
Another prior art method has included the synthesis of potassium superoxide by subjecting solid potassium hydroxide to an electric discharge sustained in oxygen yielding an 80.5% conversion. This method involves a direct current discharge at 1100 to 1200 volts and a pressure of 0.5 torr and a discharge power of 500 watts. This process has a number of disadvantages since it requires the use of high voltage and discharge power to sustain the discharge. In addition, in direct current discharge the electrodes are in direct contact with the discharged gas, in this case oxygen which results in sputtering of the electrodes resulting in the sputtered electrode particles contaminating the surperoxide product.
Other prior art methods has involved the synthesis of potassium superoxide from the oxidation of metallic potassium in liquid ammonia, the oxidation of the lower oxides of potassium and the disproportionation of potassium peroxide diperoxyhydrate (K.sub.2 O.sub.2.2H.sub.2 O.sub.2). However, all the prior art methods for the production of superoxide have either not provided a sufficiently pure superoxide or have involved use of expensive chemicals or a large number of expensive and elaborate processing steps.